In a lift system operated by a piston cylinder, especially in a vehicle lift system, if the hydraulic pressure is reduced, for example, due to a defect in a sealing element or a packing or due to a damage to a pipe, the carriages may lower suddenly and the object lifted may drop. Such an accident may kill the operator of the lift system.
Heretofore, in the field of vehicle lifts, such a danger has been eliminated by connecting a vertical rack 7' to each post of the lift and mounting a locking member 10 on the carriage which is adapted to engage the rack to prevent the carriage from lowering in case of a reduction of the hydraulic pressure. A lever is connected to the locking member 10 for manually disengaging the member 10 from the rack.
In the conventional mechanism for preventing a carriage from lowering, however, since the locking member 10 is mounted on the carriage, the lever connected to the member 10 is vertically moved together with the carriage, and when the carriage is in its uppermost or lowest position, the lever is not easy to operate. Also, when the vehicle is being lifted, the carriage with the locking member may be inclined due to the weight of the vehicle with the result that the locking member may be disengaged from the rack. Also, a complex interlocking mechanism is required to simultaneously disengage the vertically-movable locking members mounted on the respective carriages from the associated racks in given levels.